Typically, when a SQUID sensor used for a 160 channel-magnetoencephalography (MEG) system or the like is adjusted, removing noise occurring in a digital signal is a very important issue.
This is because when a spark signal occurring at an edge portion of the digital signal occurs around a SQUID sensor, the SQUID sensor may malfunction due to the spark signal affecting an analog circuit controlling the SQUID sensor as noise. When the SQUID sensor is exposed to an external spark signal, a sensing operation thereof becomes unstable since the SQUID sensor deviates from an optimal operation state or a flux trap phenomenon occurs. In addition, when some of spark flux flow into the SQUID sensor during measurement, accurate measurement is difficult.